PROJECT SUMMARY/ABSTRACT Significant growth in the number of cancer patients, particularly those ?65 years, is predicted within the U.S over the next 20 years. The majority of these patients will enter into a prolonged post-treatment survivorship phase of care. However, we are currently facing unprecedented challenges in survivorship care delivery. Serious gaps in the care of survivors have been identified, including underuse of guideline-recommended cancer surveillance services, such as annual mammography for breast cancer survivors and colonoscopy for colorectal cancer (CRC) survivors, and underuse of recommended preventive care services such as vaccinations, lipid testing and cardiovascular risk management, and disease screenings. Compounding these issues, our current oncology workforce is insufficient to care for the rapidly growing population of survivors. Primary care provider (PCP)-led survivorship care is a feasible model of survivorship care. In observational studies, survivors who receive care that involves PCPs received higher quality of care; international randomized trials comparing PCP-led to oncology-led survivorship care have shown no significant differences in time to detection of cancer recurrence or quality of life for early-stage survivors. However, there is a paucity of high-quality research on models of survivorship care in the U.S, particularly in community-based settings, seriously limiting our ability to provide high-quality cancer survivorship care. To address these issues, we will conduct a prospective cluster randomized trial of two models of cancer survivorship care in early-stage, low- risk breast cancer and CRC survivors cared for in a community-based, integrated health care setting. Building on our pilot work and drawing on the empirical literature, we will test the efficacy of an embedded PCP model (experimental condition) in which PCPs are embedded within an oncology practice and will care for low-risk survivors who will be transitioned at 12 months post-treatment. These PCPs will be given training in cancer survivorship care focused on cancer surveillance and chronic disease prevention. This model will be compared to the extant oncology physician model (usual care) that is the default condition in this healthcare system. The primary outcome will be receipt of guideline-recommended care (e.g., cancer surveillance, preventive care), assessed over a 36-month period. Secondary outcomes will include patient-reported outcomes using validated measures of patient-provider communication, care coordination, quality of life, self-efficacy in managing care, and other measures. We will also compare utilization of unplanned care (hospitalizations, urgent care) and receipt of non-recommended care. We will explore PCP perceptions of confidence in delivery of survivorship care. We will conduct this trial in 8 large, hospital-based medical centers of an integrated health care system, Kaiser Permanente Southern California, with approximately 2,000 early-stage breast and CRC survivors. Our results will provide more definitive evidence on the effectiveness of a scalable model of PCP-led survivorship care, addressing the critical shortage of oncology providers while maintaining or improving quality.